Thread cutting device for sewing machine



July 30, 1968 KATSUTOSHI YAMAGUCHI 3,

THREAD CUTTING DEVICE; FOR SEWING MACHINE 2 Sheets-Sheet 1 Filed May 3, 1965 F] 5- 2 Ff6' 3 Mid Jaka- July 30, 1968 KATSUTOSHI YAMAGUCHEI THREAD CUTTING DEVICE FOR SEWING MACHINE 2 Sheets-Sheet 2 Filed May 5, 1965 I NVEN TOR. K4 73 U 7' 06 H yflMfiGUCf/l United States Patent 3,394,670 THREAD CUTTING DEVICE FOR SEWING MACHINE Katsutoshi Yamagnclii, Koganei-shi, Japan, assignor to Janome Sewing Machine Co., Ltd., Tokyo, Japan Filed May 3, 1965, Ser. No. 452,477 Claims priority, application Japan, May 6, 1964, 39/34,978 Claims. (Cl. 112-252) ABSTRACT OF THE DISCLOSURE The lower portion of the presser bar of a sewing machine is provided with a rearwardly facing concave recess forming an arcuate concave cutting edge with a flat lateral face of the presser bar so that threads can be cut by moving the threads downward over the cutting edge.

The present invention relates to sewing machines in general, and more particularly to an improved thread cutting device which may be utilized in such machines.

It is an important object of the present invention to provide a very simple, compact, practical and inexpensive thread cutting device which, in addition to cutting threads, can perform at least one additional function.

Another object of the invention is to provide a cutting device which may be used to sever one or more threads at a time, which is mounted in the sewing machine in such a way that it is highly unlikely to cause accidental damage to the fabric which is being worked upon, which is equally unlikely to accidentally sever a thread, and which is installed at a point where it cannot obstruct or impede the operation of other parts and is least likely to injure the operators fingers.

A further object of the invention is to provide a thread cutting device of the above outlined characteristics which is sufiiciently close to the needle to be capable of severing the thread in immediate proximity to the Work.

An additional object of the present invention is to provide a thread cutting device which is sufficiently inexpensive to warrant its use not only in commercial sewing machines but also in machines which are intended for domestic use.

A concomitant object of the instant invention is to provide a thread cutting device whose cutting edge or edges are configurated in such a way that they are not likely to undergo localized wear, wherein such cutting edge or edges will automatically compel one or more tensioned threads to slide therealong and to be severed, not by tearing but with a clean severing action.

Still another object of the invention is to provide a thread cutting device of the above outlined characteristics which may be produced as an integral part of an essential component of the sewing machine and which may be produced simultaneously with such essential part.

Another object of the invention is to provide a thread cutting device which can be utilized by skilled operators as well as by less skilled persons, and which does not detract from the eye-pleasing appearance of the sewing machine.

Briefly stated, one feature of my invention resides in the provision of an elongated presser bar having an end portion which is arranged to carry the customary presser foot and which is also provided with one or more cutting edges sharp enough to sever at least one tensioned thread at a time. The cutting edges are located at a level above the presser foot but below the supporting head in which the presser bar is reciprocably mounted in a manner known per se.

In accordance with a preferred embodiment of my invention, a cutting edge may be provided along the innersection of two mutually inclined vertical faces partially bounding the lower end portion of the presser bar. One of these faces (preferably that face which is the rear face when the presser bar is mounted in a sewing machine) is provided with a transversely extending substantially horizontal recess or cutout which is bounded by a concave or substantially concave surface meeting the other face along an arcuate cutting edge.

Thus, the presser bar of my invention constitutes a component which performs two functions, namely, the function of carrying the presser foot and the additional function of serving as a thread cutting device. The recess in the presser bar can be made shallow so that the provision of such recess does not unduly weaken the presser bar. Also, the recess is preferably provided in a rather narrow rear face of the presser bar so that the bar is weakened in a direction coinciding with the maximum cross-sectional dimension of its lower end portion.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved thread cutting device itself, however, both as to its construction and the best mode of using the same, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of a specific embodiment with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary perspective view of the sewing station in a sewing machine which embodies the thread cutting device of the present invention;

FIG. 2 is an enlarged front elevational view of the lower portion of a presser bar which forms part of the sewing machine shown in FIG. 1 and which is integral with the thread cutting device of my invention;

FIG. 3 is an enlarged side elevational view of the structure shown in FIG. 2;

FIG. 4 is a horizontal section as seen in the direction of arrows from the line IV-IV of FIG. 2;

FIG. 5 is a perspective view of a portion of the structure shown in FIG. 1, as viewed from a different direction, and illustrates the manner in which the thread cutting device is put to use; and

FIG. 6 is a fragmentary perspective view of a presser bar which is provided with a conventional thread cutting device.

Referring first to FIG. 1, there is shown the sewing station of a sewing machine which comprises a hollow supporting head 11 carrying a downwardly extending needle bar 1 and a vertical presser bar 2 which is adjacent to the needle bar 1. The needle bar 1 carries a thread guide 5 and detachably supports an eye-pointed needle 4 which is secured thereto by a fixture here shown as a clamping band 3.

The lower end portion of the presser bar 2 is detachably connected with a presser 6 whose bifurcated foot 16 straddles the needle 4 when the latter is caused to perform a working stroke. The means for attaching the presser 6 to the lower end portion of the presser bar 2 comprises a screw 7. A conventional control lever 8 is pivotably mounted in the supporting head 11 and is utilized to raise or lower the presser bar 2 in a well known manner. When the control lever 8 assumes the position whichis shown in FIG. 1, the cloth or fabric which is supported by a bed plate or base plate 12 is pressed against the upper side of a throat plate 9. The lower end portion of the presser bar 2 is formed with a flat vertical side face 15 to make sure that the presser 6 cannot rotate thereon when the screw 7 is drawn tight. The external threads of the screw 7 can be moved into mesh with the threads of a tap'ped bore 17 which is provided in the lower end portion of the presser bar 2 and whose axis is preferably normal to the plane of the flat side face 15, see FIGS. 2 and 3.

In accordance with my present invention, the lower end portion of the presser bar 2 is formed with a transversely extending horizontal trough-shaped recess which is bounded by a concave surface and which is formed in a vertical rear face a of the presser bar 2. The concave surface bounding the recess 10 intersects and defines with the side face 15 an arcuate recessed cutting edge 20. This cutting edge may be utilized to sever one or more threads in a manner to be described in connection with FIG. 5. FIG. 4 shows that the faces 15 and 15a make an obtuse angle and that the face 15 makes a right angle with a vertical plane which is tangential to the deepmost zone of the recess 10. However, it will be readily understood that the recess 10 may be bounded by a concave surface whose deepinost zone need not be normal to the side face 15 but may enclose therewith an obtuse or acute angle. Also, it is possible to make the edge 15b or 150 sharp enough to be used as a cutting edge. The edge 15b is vertical and extends along the intersection of the faces 15, -15a. The edge 15c is also vertical and extends along the intersection between the side face 15 and a front face 15d. At this time, I consider it more practical to make the arcuate edge at the intersection of the surface bounding the recess 10 with the side face 15 sharp enough to serve as a cutting edge. It will be seen that the lower end portion of the presser bar 2 performs the function of detachably supporting the presser 6 and the additional function of a cutting device for thread. Thus, the cutting device is integral with the presser bar and is preferably located in a zone wherein it is least likely to injure the hand of the operator, to damage the cloth or fabric which is being worked upon, and/or to accidentially cut the thread.

The expenses involved in providing the lower end portion of the presser bar 2 with the cutting edge 20 are minimal, and the recess 10 may be machined into this bar at the time the latter is being made so that the provision of the cutting edge 20 requires no separate setup or other costly operation. If desired, the cutting edge 20 may be sharpened from time to time, but the material of the presser bar 2 is normally hard enough to provide a sharp cutting edge which is not likely to become dull. The presser bar 2 may be made of tool steel. The arcuate shape of the cutting edge 20 insures that .the thread will slide therealong during severing so that the full length of the cutting edge may be used to perform a cutting operation.

FIG. 5 illustrates the manner in which two threads 13 and 13' are held by two fingers of each hand and are caused to move toward and to slide along the cutting edge 20. The cut will be made across such portions of the threads 13 and 13 which are indicated by the arrow B. Thus, all that is necessary is to move one or more threads relative to the presser bar 2 and to exert a pull on such portions of the threads which are located at the opposite sides of the presser bar while the threads slide along the cutting edge 20. The recess 10 is preferably provided at such a distance from the presser 6 that the cutting edge 20 is accessible in each end position of the presser bar 2, i.e., regardless of whether the control lever 8 assumes the end position shown in FIG. 1 or the other end position in which it maintains the presser bar in raised position.

While it is equally possible to provide the presser bar 2 with a cutting edge which extends beyond the outlines of the lower end portion of this bar, the construction of the presser bar 2 as shown in FIGS. 1 and 5 is preferred because the cutting edge is located within the confines of the presser bar and is less likely to cause injury to the fingers of a careless operator, to cause damage to the fabric and/or to accidentially cut the thread 13 and/or 13. The provision of the recess 10 does not in any way detract from the appearance of and does not unduly weaken the presser bar.

In order that the advantages of the presser bar 2 will be more readily understood, I have shown in FIG. 6 a portion of a conventional presser bar 25 which carries a thread cutting device 14 of known design. The cutting device 14 is made of sheet steel stock and comprises a sleeve 14" which surrounds a cylindrical portion of the presser bar 25. The cutting edge of the device 14 is shown at 14'. Not only is the cutting device 14 likely to slide along the presser bar 25, but it also constitutes a separate part which must be produced in a separate machine and must be mounted on the presser bar. The cutting edge 14 extends from the periphery of the presser bar 25 and, therefore, is much more likely to injure the hand of the operator and/or to cause damage to fabric or to accidentally sever the thread. In order to cut the threads 13 and 13, the operator must introduce such threads into the loop formed by the cutting device 14, and the threads are thereupon pulled downwardly to be severed along the cutting edge 14'. An inexperienced operator or a person whose vision is not very sharp will find it difficult and timeconsuming to make a cut by resorting to the device 14 of FIG. 6. Also, the cut is normally made by the central portion of the cutting edge 14; therefore, such central portion of the cutting edge will become dull and will tend to tear rather than to make a clean cut across one or more threads.

Many conventional sewing machines are without cutting devices for threads. In order to sever a thread, the user must resort to scissors, razor blades and/or knives. Such separate cutting implements are likely to be misplaced, to injure the users hand and/or to be accidentally concealed beneath the fabric so that the user must waste time to locate the cutting implement whenever he or she desires to cut the thread.

It is also known to provide a rotary cutting blade which is mounted below the bed plate and which may be driven by the motor of a sewing machine in response to actuation of a coupling member. Such cutting blades are very costly and they are less readily accessible than the cutting device of my invention. Due to their high initial cost, such rotary cutting blades are to be found in certain commercial sewing machines but they are too expensive for use in sewing machines for domestic use. The cutting device of my present invention can be utilized in commercial and/or household sewing machines because its manufacturing cost is minimal. In fact, conventional presser bars of existing sewing machines may be readily replaced by presser bars of the type shown in FIGS. 1 to 5 so that such existing machines may be provided with exceptionally simple, long-lasting and properly shielded cutting devices at a minimal cost.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a sewing machine, a supporting head; and a vertical presser bar extending downwardly from said head, said presser bar having a lower end portion provided with a trough-shaped recess forming in said presser bar with the surface thereof a recessed thread cutting edge.

2. In a sewing machine, a supporting head; and a vertical presser bar extending downwardly from said head, said presser bar having a lower end portion provided with a trough-shaped receding face and a vertical face intersecting said trough-shaped receding face, said faces thus defining between themselves a recessed cutting edge sharp enough to form a cut across a thread when such thread is subjected to tensional stresses and is caused to slide along the cutting edge.

3. In a sewing machine, a supporting head; a presser bar; and means reciprocably mounting said presser bar in and extending substantially vertically downwardly from said head, said presser bar having a lower end portion provided with two intersecting substantially vertical faces, one of said faces having a transverse recess bounded by a concave surface meeting the other of said faces along an arcuate cutting edge which is sharp enough to sever at least one thread at a time.

4. In a sewing machine, a supporting head; a presser bar; and means reciprocably mounting said presser bar in and extending substantially vertically downwardly from said head, said presser bar having a lower end portion provided with two intersecting substantially vertical faces, one of said faces having a transverse recess bounded by a concave surface meeting the other of said faces along an arcuate cutting edge which is sharp enough to sever at least one thread at a time; and means for reciprocating said presser bar between an upper end position and a lower end position through strokes of such length that said lower end portion of the presser bar extends beyond said supporting head in each end position of the presser bar whereby the cutting edge is accessible for severing of threads regardless of the position of said presser bar.

5. In a sewing machine, a supporting head; a presser bar; and means mounting said presser bar in and extending substantially vertically downwardly from said head, said presser bar having a lower end portion bounded by two mutually inclined vertical side faces, one of said side faces having a transversely extending recess bounded by a con-cave surface meeting the other of said faces along an arcuate cutting edge, said recess having a deepmost zone and said other face making an acute angle with a vertical plane which is tangential to said deepmost zone of the recess.

6. In a sewing machine, a supporting head; a presser bar; and means mounting said .presser bar in and extending substantially vertically downwardly from said head, said presser bar having a lower end portion bounded by two mutually inclined vertical side faces, one of said side faces having a transversely extending recess bounded by a concave surface meeting the other of said fac'es along an arcuate cutting edge, said recess having a deepmost zone and said other face making an obtuse angle with a vertical plane which is tangential to said deepmost zone of the recess.

7. In a sewing machine, a supporting head; a presser bar; and means mounting said presser bar in and extending substantially vertically downwardly from said head, said presser bar having a lower end portion bounded by two mutually inclined vertical side faces, one of said side faces having a transversely extending recess bounded by a concave surface meeting the other of said faces along an arcuate cutting edge, said recess having a deepmost zone and said other face making a right angle with a vertical plane which is tangential to said deepmost zone of the recess.

8. As a novel article of manufacture, an elongated presser bar for use in sewing machines, said presser bar having an end portion partially bounded by a flat face located in a plane which is parallel with the axis of said bar and a second face which intersects said flat face, said second face having a transversely extending recess bounded by a substantially concave surface meeting with said flat face along an arcuate cutting edge.

9. A presser bar as set forth in claim 8, wherein at least said end portion consists of tool steel.

10. A presser bar as set forth in claim 8, wherein said second face is the rear face of said end portion when the presser bar is installed in a sewing machine.

References Cited UNITED STATES PATENTS 287,197 10/1883 Valero 112-252 2,372,609 3/1945 Silverman 112-252 X 2,445,629 7/1948 Newton 112-252 2,781,012 2/1957 Kuhar 112-252 3,106,902 10/1963 Foltis et al. 112-252 3,158,117 11/1964 Samuels 112-252 2,606,364 8/ 1952 Gustafson 30-355 XR 2,671,267 3/1954 Michalek 30-355 FOREIGN PATENTS 891,245 9/ 1953 Germany.

JORDAN FRANKLIN, Primary Examiner.

J. R. BOLER, Assistant Examiner. 

